Field of the Invention
The present invention relates to a method of producing a wave gear device, by which a circular spline, a flex spline, and a wave generator are positioned, and relates to a wave guide device.
Description of the Related Art
Wave gear devices, with which high speed-reduction ratios can be obtained despite their comparatively small sizes, are widely used for speed reducers of motors for driving articulations of robot arms. The wave gear device includes three main components and five positioning components, which position the three main elements.
The three main components are an internal gear referred to as a circular spline, an external gear referred to as a flex spline, and an elliptical cam member referred to as a wave generator. The circular spline is an annular rigid gear having teeth on its inner side. The flex spline is a thin flexible annular gear having teeth on its outer side. Two of the five positioning components are a housing and an output member. The circular spline is fastened to the housing. The flex spline, which is an output of the wave gear device, is fastened to the output member. The other three of the five positioning components are a cross roller bearing disposed between the housing and the output member, a bearing that holds rotation of the wave generator, and a support member that holds the bearing and is fastened to the housing.
Here, it is known that accuracy with which the circular spline, the flex spline, and the wave generator are attached significantly affects rotational accuracy of the wave gear device. Accordingly, it is required that components such as a housing be highly accurately processed in the related art. Thus, when securing the circular spline to the housing, it is required that the flatness and the parallelism of the attachment surface be highly accurately realized. Also, when securing the flex spline and the wave generator, it is required that the coaxiality of the axis of the circular spline secured to the housing and the axes of the flex spline and the wave generator be highly accurately realized.
Japanese Patent Laid-Open No. 2009-257409 has proposed a method of assembling a wave gear device in which a circular spline, a flex spline, and a wave generator are positioned with an inner circumferential surface of a housing as a reference surface by using a jig.
An articulated multi-axis robot arm includes a plurality of articulations, in each of which a drive motor and the wave gear device are disposed. Thus, when attachment accuracy of the circular spline, the flex spline, and the wave generator of the wave gear device is poor in each articulation, the axes of the components become misaligned and inclined, and rotational accuracy is degraded. This significantly degrades the performance of the robot arm (JIS B 8432: Manipulating industrial robots-Performance criteria and related test methods). That is, for the wave gear device, it is important to highly accurately align the central axes of the circular spline, the flex spline, and the wave generator, which are the main components of the wave gear device.
However, according to the Japanese Patent Laid-Open No. 2009-257409, the circular spline, the flex spline, and the wave generator are positioned with reference to the housing. Thus, it is required that the reference surface of the housing, in addition to the circular spline, the flex spline, and the wave generator, are highly accurately processed and produced. Accordingly, since the housing is highly accurately processed and produced, the cost and time required for producing the wave gear device are increased.
In particular, according to the Japanese Patent Laid-Open No. 2009-257409, a reference surface for the circular spline and a reference surface for the jig used to position the flex spline need to be formed on the inner circumferential surface of the housing. As the area of the reference surface increases in the housing, the cost and time required for processing and producing the housing tend to increase. Thus, according to Japanese Patent Laid-Open No. 2009-257409, the cost is increased since it is required that the reference surface of the housing be large.
When time and the cost are reduced by degrading accuracy of the reference surface of the housing, misalignment of the axes of the circular spline, the flex spline, and the wave generator is increased.